Generally, when image information is stored into a memory, gray scale levels of respective pixels are obtained as numerical values and the data is stored in a predetermined order in continuous memory areas.
Further, the data string format upon storage of pixel information into memory differs in accordance with format or implementation of data processing algorithm of device to input images to a frame memory or device to output images from the memory, however, memory access is always made in accordance with the same procedure inside the device.
That is, when pixel information stored in a particular address is accessed, the same address value is always used.
Accordingly, in an image processing apparatus having a conventional storage device, there is a strong linkage between the content of the frame memory and an original image. In this case, if the content of the frame memory can be obtained or referred to by any means, the original image can be comparatively easily reproduced even though the procedure upon image data generation is not known.
However, this fact is very inconvenient in consideration of image information security.
For example, when the content of frame memory is stored in a file in another place or transferred to another place via a network, a third person may have an opportunity to access the image data during such data transfer which is often performed as daily work. As a result, there is a high probability that the image data is reproduced and the content of the original image is known.
Generally, confidential documents and the like are encrypted for protection of the contents. However, encryption is generally complicated and time-consuming processing, and further, installation of the encryption processing program is often difficult.